Heat exchanger channel

ABSTRACT

A fluid flow channel for a heat exchanger, the channel comprising an elongate tubular channel body extending along an axis A from a first end to a second end, the channel body having walls, the interior surface of which define an interior channel through which heat exchanger fluid flows from the first end to the second end, and wherein the channel body comprises two or more straight sections having a constant cross section in which the interior channel has a rectangular, square or triangular cross-section, and a twisted section between the or each pair of adjacent straight sections, in the axial direction, the twisted section being a section resulting from one of the straight sections twisted about the axis A with respect to an adjacent straight section.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No.22461580.7 filed Jul. 13, 2022, the entire contents of which isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure is concerned with channels for the flow of fluidin a heat exchanger, and specifically channels made by additivemanufacturing.

BACKGROUND

Heat exchangers typically work by the transfer of heat between fluidflowing in parallel channels defined by metal plates of a heat exchangercore. A heat exchanger core is generally in the form of a block made upof layers of plates which define the channels through which the fluidflows. The channels are arranged such that hot fluid flows through somechannels and cold fluid flows through other channels with the hot andcold channels arranged either vertically or horizontally adjacent eachother such that heat is exchanged across the boundary between thechannels. Thermal properties are improved by the introduction ofturbulence in the flow channels and so, conventionally, a heat exchangercore comprises corrugated metal plates arranged adjacent each other soas to define corrugated flow channels for the heat exchange fluids.

Additive manufacture, or 3D printing, has recently become a preferredmanufacturing method for many parts and components due to the fact thatit is relatively quick and low cost and allows for great flexibility inthe design of new components and parts. Due to the fact that componentsand parts made by additive manufacture (AM) can be quickly made in acustom designed form, as required, AM also brings benefits in thatstocks of components do not need to be manufactured and stored to beavailable as needed. AM parts can be made of relatively light, butstrong materials. As AM is becoming more popular in many industries,there is interest in manufacturing heat exchangers using AM.

In conventional heat exchanger channels, the viscous fluids that arecommonly used create a thick boundary layer at the walls of thechannels. This boundary layer presents a resistance to heat exchangeacross the channel walls and reduces the amount of energy that can betransferred through the channel wall by heat exchange. Additivemanufacturing provides the opportunity to create new shapes of heatexchanger channel to address this problem.

SUMMARY

According to this disclosure there is provided a channel for a heatexchanger, through which heat exchange fluid flow will flow, in use, thechannel comprising an elongate tubular channel body extending along anaxis A from a first end to a second end, the channel body having walls,the interior surface of which define an interior channel through whichheat exchanger fluid flows from the first end to the second end, andwherein the channel body comprises two or more straight sections havinga constant cross section in which the interior channel has arectangular, square or triangular cross-section, and a twisted sectionbetween the or each pair of adjacent straight sections, in the axialdirection, the twisted section being a section resulting from one of thestraight sections twisted about the axis A with respect to an adjacentstraight section, wherein at the twisted section the interior channelhas a cross-section different from the cross section at the adjacentstraight section, thus creating a swirl effect on fluid flowing throughthe interior channel.

Also provided is a heat exchanger, and a method of manufacturing achannel for a heat exchanger.

BRIEF DESCRIPTION

Examples of heat exchanger channels and methods of making them,according to the disclosure, will be described with reference to thedrawings. It should be noted that variations are possible within thescope of the claims.

FIG. 1 is a three dimensional view of an example of a channel accordingto the disclosure.

FIG. 2 is a side view of a channel such as shown in FIG. 1 .

FIG. 3 shows a section of the channel of FIG. 1 .

FIG. 4 is an end view of a channel such as shown in FIG. 1 .

FIG. 5 shows the effect of the channel design on fluid flow through thechannel.

FIG. 6 shows an example of a heat exchanger core having such channels.

DETAILED DESCRIPTION

Typically, a heat exchanger comprises a plurality of fluid flow channelsdefined between layers of metal plates and through which heat exchangefluids flow. The fluids are provided to the core of plates and channelsvia a manifold such that a relatively cold fluid flows through some ofthe channels and a relatively hot fluid flows through others of thechannels. The channels are arranged such that their outer walls are incontact with outer walls of other channels such that heat exchange takesplace across the adjacent channel walls due to the different temperatureof the fluids flowing through the channels. As mentioned above,conventionally, the channels have been formed by corrugated sheets withthe corrugations forming the channels. With the advent of additivemanufacturing techniques, however, it has become possible to formchannels of different shapes and/or as discrete tubular elements thatare assembled side-by-side to form the heat exchanger core. Tubularchannels may be, for example, in the form of a rectangular cross-sectiontube or a triangular cross-section tube.

It is known that the convective heat transfer coefficient can beimproved by introducing turbulence in the flow through the channel. Inparticular, creating turbulence avoids creation of the insulatingboundary layer at the channel walls, as mentioned above. Again, theincreasing use of additive manufacturing has made it possible to createchannels having features that increase turbulence in the flow.

Additive manufacturing of channels does, however, bring its ownlimitations in that there is a limitation of channel size due to therequired post-printing powder removal. It is often desired to createdesigns with features inside the channels but which have limited impacton the cross-sectional area of the channel to avoid the accumulation ofpowder, and it is not easy to incorporate additional devices for causingswirl of the fluid as it travels through the channel into the interiorof the channel within such constraints.

The channel according to this disclosure is formed using additivemanufacture and so is limited in size, but is structured to provide aswirl effect that does not reduce the cross-sectional area of thechannel, or only reduces the cross section by a limited amount and sodoes not hinder powder removal or flow of fluid, but does increaseturbulence of the fluid flowing through the channel.

The channel according to this disclosure, an example of which is shownin various views in FIGS. 1 to 4 , comprises an elongate tubular channelbody 10 extending along an axis A from a first end 11 to a second end12. The channel body defines an interior channel 14 through which heatexchanger fluid flows from the first end 14 a to the second end 14 b,and wherein the body comprises two or more straight sections 20 having aconstant cross section wherein the interior channel has a rectangular,square or triangular cross-section, and a twisted section 30 between theor each pair of adjacent straight sections, in the axial direction, thetwist section being a section resulting from one of the straightsections twisted substantially 90 degrees (for a square channel) or 180degrees for a rectangular channel or 60 degrees for a triangular channelwith respect to the adjacent straight section, wherein at the twistsection the interior channel has a cross-section 32 different from thecross section at the straight section, thus creating a swirl effect onfluid flowing through the channel.

In practice, the channel will be formed with several twist sections 30,each adding a further 90/180/60 degree twist of the channel body. Aftereach twist, then, the cross-section of the straight section 20 isaligned with that of the previous straight section, before the twist.

The twists between straight sections thus cause an interruption in thestraight channel for the fluid flowing through the channel.

The fact that the swirl effect is formed by the channel body—i.e. in thewall of the channel, also means that this effect is actually created atthe location where the boundary layer effect is a particular problem.

The channel is made, as mentioned above, by additive manufacturing or 3Dprinting. This means that the positions of the twist sections and,hence, the lengths, L1, of the straight section, can be varied asdesired, e.g. depending on the flow conditions, temperature, pressure,fluids etc. for the heat exchanger for which the channel is made. Thelength L2 of the twist section (essentially the pitch of the run) canalso be varied as desired. The lengths can be varied to vary theintensity of the swirl effect.

The swirl effect of the twists can be seen in FIG. 5 . Fluid initiallyflows along a straight section and then hits a twist section whereuponthe fluid is subjected to a swirl effect changing its velocity. This isfollowed by a straight channel and, depending on the length and designof the channel, subsequent twist sections. The swirl has the effect ofdisrupting the boundary layer at the channel inner surface due to thechanges in surface geometry. The resulting boundary layer is thereforemuch thinner than the boundary layer that results in straight channels,thus resulting in improved heat transfer.

As seen, for example, in FIG. 6 , a plurality of such channels 10 can beassembled into a block to form a core 100 of a heat exchanger. In theexample shown, all channels have the same design. It is also feasiblethat channels of different designs could be used in the core.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

1. A fluid flow channel for a heat exchanger, the channel comprising: anelongate tubular channel body extending along an axis A from a first endto a second end, the channel body having walls, the interior surface ofwhich define an interior channel through which heat exchanger fluidflows from the first end to the second end, and wherein the channel bodycomprises: two or more straight sections having a constant cross sectionin which the interior channel has a rectangular, square or triangularcross-section, and a twisted section between the or each pair ofadjacent straight sections, in the axial direction, the twisted sectionbeing a section resulting from one of the straight sections twistedabout the axis A with respect to an adjacent straight section, whereinat the twisted section the interior channel has a cross-sectiondifferent from the cross section at the adjacent straight section, thuscreating a swirl effect on fluid flowing through the interior channel.2. A fluid flow channel as claimed in claim 1, wherein the two or morestraight sections have a constant rectangular cross-section.
 3. flowchannel as claimed in claim 1, wherein the two or more straight sectionshave a constant triangular cross-section.
 4. A fluid flow channel asclaimed in claim 1, wherein the two or more straight sections have aconstant square cross-section.
 5. A fluid flow channel as claimed inclaim 4, wherein each straight section is twisted at the twist sectionby 90 degrees with respect to its adjacent straight section.
 6. A heatexchanger core comprising: one or more fluid flow channels as claimed inclaim
 1. 7. A heat exchanger core as claimed in claim 6, comprising aplurality of fluid channels arranged adjacent each other to form ablock.
 8. A heat exchanger comprising: a heat exchanger core as claimedin claim
 6. 9. A method of forming a fluid flow channel for a heatexchanger using additive manufacture, the method comprising: forming afirst straight section of am elongate tubular channel body having achannel therethrough with a constant cross-section; creating a twistedsection being twisted relative to the first straight section, thetwisted section having a cross section different from that of the firststraight section; and creating a second straight section axially alignedwith the first straight section and having a constant cross-section, thetwist creating a swirl effect on fluid flowing through the channel. 10.A method as claimed in claim 9, wherein each twisted section creates atwist of 90 degrees between a straight section and an adjacent straightsection.
 11. A method of forming a heat exchanger core, comprising:forming a plurality of fluid flow channels according to the method ofclaim 9; and arranging the plurality of fluid flow channels adjacenteach other to form a block.
 12. The method of claim 11, furthercomprising: providing a first fluid inlet, a first fluid outlet, asecond fluid inlet and a second fluid outlet, the first fluid inlet andthe first fluid outlet connected, respectively, to first and second endsof a first set of the plurality of fluid flow channels and the secondfluid inlet and the second fluid outlet connected, respectively, tofirst and second ends of a second set of the plurality of fluid flowchannels.
 13. The method of claim 12, comprising assembling the firstplurality of flow channels adjacent each other in a first layer and thesecond plurality of fluid flow channels adjacent each other in a secondlayer.
 14. The method of claim 12, comprising assembling the first andsecond plurality of flow channels adjacent each other in a first layersuch that each one of the first plurality of fluid flow channels islocated between two of the second plurality of fluid flow channels.